The disposable bioreactors were considered a novelty, and perhaps even a passing trend, as recently as mid 90ties. As single-use bioreactors have matured and begun to address most of these issues, their market acceptance has rapidly expanded. The move to disposable bioreactors is, in many instances, driven by reduction in sterilisation and cleaning requirements, improved plant flexibility, reduced costs and faster time to market for the end product. All of these benefits have been recently documented. These hurdles include the ability to add reliable, accurate, low cost sensors and pumping devices so that standards can be generated and the process repeatability readily documented.
The New Brunswick Scientific in the US and other manufactures stirred-tank bioreactor systems circulates the nutrient internally by a rotating centrifugal pump head submersed into the nutrient. The mechanical shaft connects the impeller to an electrical motor placed outside on top of the bioreactor. ATMI-Life Science, Artelis both in Belgium, Sartorius-Stedim in Germany, LevTech in the US and other suppliers of disposable plastic bags includes a mixing device inside at the disposable plastic bag bottom. Magnetic forces transfer the rotating force from an external mounted drive arrangement eliminating rotating axles penetrating the bag wall. As there is always a magnet in the rotating device, it is not a fully disposable pump system.
The use of tube pumps, peristaltic pumps like from US company Watson Marlow is the closest one gets to single-use pumps in the pharmaceutical industry with limited mass transfer capacity. Further the typical peristaltic pump of reasonable capacity is very expensive. No manufacturer offers a 100% single-use, disposable diaphragm pump for low energy consumption during operation at low initial cost.
Traditional diaphragm pumps are typically twin-membrane pneumatic operated and free-wheeling with no media to pump or changes in media viscosity. No pumps are known with electronic control of operation, such as variable stroke, variable strokes frequency independent of pumped media viscosity or ability to handle more than one fluid circuit. No disposable, electronically controlled diaphragm pump is available from important suppliers such as German DEPA/Crane, US based Wilden, Trebor or Swedish companies like Kelva and Dominator.
A diaphragm pump is a positive displacement pump that typically uses a combination of the reciprocating action of a rubber, thermoplastic, elastomeric or even Teflon diaphragm and suitable non-return check valves to pump a fluid. Sometimes this type of pump is also called a membrane pump. When the volume of a chamber is increased (the diaphragm moving), the pressure on the inlet valve(s) decreases, and fluid is drawn into the chamber. When the chamber pressure later increases from decreased volume (the diaphragm moving), the fluid previously drawn in is discharged through the exhaust valve(s). Finally, the diaphragm moving once again draws fluid into the chamber, completing the reciprocating cycle. The pump principle offers gently conveyance of liquids and is ideal for a sensitive media. The known diaphragm pumps have no measures built in for tracking the actual volume being pumped and are further depending on on/off valves with no one taking advantage of proportional valves for membrane position regulation.
Within the pharmaceutical, chemical and dairy industry, the diaphragm pump has been used intensively for hundred years or more in a variety of configurations. Though all diaphragm pumps are of non-integrated, independent design and open installation, they all demand regular maintenance in long time use in aggressive or particle filled media. The pump body is often manufactured from cast steel, stainless steel and expensive Teflon and typically the membranes are manufactured from silicone, EPDM, Teflon or the like of flexible materials.